Our long range goal is to determine the mechanisms of microtubule dependent movements, especially the movement of chromosomes during mitosis. For the next three years, I propose the following projects: (1) Isolation and characterization of the microtubule associated proteins which are responsible for cross-linking microtubules and actin filaments; (2) Identification of the energy transducing enzymes(s) required for chromosome movement by microinjection of neutralizing antibodies against dynein and myosin into living cells; (3) Measurement of the contractile protein and tubulin content of the mitotic spindle by densitometry of micrographs of cells stained with fluorescent antibodies; and (4) Localization of the actin and myosin in the mitotic spindle at the ultrastructural level using labeled antibodies and improved actin fixation techniques.